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You, Your Pets, and Parasites
For many animal caregivers, pets are an important part of the
household environment. As humans and pets co-inhabit, your family
is more likely to be exposed to internal and external parasites.
Consequently, quality family health may be determined by actions
taken to maintain your pet's well being.
"Because our pets live in an environment with many other animals
they will be constantly exposed to parasites," notes Dr. Thomas
Craig, professor of Pathobiology at Texas A&M University
College of Veterinary Medicine & Biomedical Sciences. "The
local prevalence of parasites depends on the local
"Dogs are infected by some parasites while still in the uterus,
from an activation of larvae in the mother's tissues. Both cats and
dogs also transmit parasites in the milk. For some species,
parasites enter the body by penetrating the skin or when the pet
ingests microscopic worm eggs, or cysts in the environment. Cats
generally have fewer worms but tend to have several species of
worms acquired by eating the prey they catch and devour," explains
Craig. "In central Texas the most common internal parasites of dogs
are hookworms and heartworms with a lesser number being infected
with roundworms, whipworms, tapeworms, and coccidia."
"Dogs may be infected with parasites when bitten by ticks, fleas
or mosquitoes and, additionally, by eating ticks, fleas, bugs or
beetles and other animals that have tissue forms of parasites." Dr.
Craig says that the transmission to cats is by the same means as
for dogs, but cats spend less time resting on the soil and spend
more time eating other creatures in the environment.
Internal parasites are not easy to visually detect in dogs and
cats. "About the only internal parasite the pet owner typically
sees are tapeworm segments which resemble a grain of rice in size.
They are seen in fecal material or moving on the hair." Dr. Craig
says occasionally a worm will be vomited and the animal may have
clinical signs such as coughing, white mucous membranes, tires
easily or a bloody stool --- all may indicate parasites. However,
other things can cause these same signs so most infections are not
obvious to the average person.
Your veterinarian should be able to run fecal and blood samples
from your pet to determine if there are internal parasites. These
should be part of your pet's annual checkup.
"External pet pests, such as fleas, generally are of little
significance to human health but infect pets with other parasites
such as the bacteria causing cat scratch fever, which occurs in
humans, from a cat bite, scratch or contamination of a wound by
flea feces. The most common tape worm of cats and dogs is acquired
by eating fleas and occasionally occurs in young children." Craig
notes that if flea infested pets have been in an environment but no
longer are present, then fleas will gladly feed on humans.
"As pets get older they become resistant to some types of
parasites but not others. Therefore, parasite control will be
required throughout the life of the pet. Continuing prophylactic
treatment is especially important with heartworms which can be
transmitted by mosquitoes every month of the year, depending on the
"Humans become infected by parasites of pets by walking barefoot
or gardening without gloves in soil where a dog has defecated weeks
earlier or by eating eggs or cysts deposited by a cat or dog in the
environment for up to two years previously." Humans also share
parasites transmitted by ticks and other invertebrates and these
can be transmitted by bites or by eating bugs, states Craig.
There are health tips that can help protect family members.
"Wear shoes and gloves in the garden, clean up the cat's litter box
daily, pick up poop! Cook or peel raw vegetables from the garden,
wash your hands after handling the pet or anything that has been in
contact with the pet."
Craig notes that prompt disposal of fecal material and wearing
protective clothing is important. "One hundred years ago hookworm
infection was common in the human population, but use of toilets
and regular wearing of shoes has eliminated the infection. Screens
keep out malarial mosquitoes, and the common roundworm and whipworm
of humans are largely controlled by toilets and personal hygiene.
If it worked in humans could it work in pets?"
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